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Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands			3 Months Ended				6 Months Ended		12 Months Ended	15 Months Ended
	Mar. 31, 2026	Oct. 31, 2025	Sep. 30, 2026	Jun. 30, 2026	Sep. 30, 2025	Jun. 30, 2025	Sep. 30, 2026	Sep. 30, 2025	Mar. 31, 2026	Sep. 30, 2026
Loss Contingencies [Line Items]
Revenues			$ 1,179,996		$ 1,140,893		$ 2,336,539	$ 2,311,947
Ligado [Member]
Loss Contingencies [Line Items]
Revenue from contract with customer, excluding assessed tax, quarterly										$ 16,000
Inmarsat [Member]
Loss Contingencies [Line Items]
Proceeds from legal settlement		$ 420,000
Contingent proceeds from legal settlements	$ 100,000								$ 568,000
Contingent legal settlement escalator							3.00%
Product [Member]
Loss Contingencies [Line Items]
Revenues			359,401		$ 319,383		$ 683,506	$ 664,067
Defense and Advanced Technologies [Member] \| Positive Outcome Of Litigation [Member] \| Product [Member]
Loss Contingencies [Line Items]
Revenues				$ 12,300		$ 30,800
Unfavorable Regulatory Action [Member]
Loss Contingencies [Line Items]
U.S. government contract-related reserves	$ 15,100		$ 13,100				$ 13,100		$ 15,100	$ 13,100